During certain types of medical surgery or treatment, an introducer is used to access the vascular system of a patient. The introducer is inserted through the wall of a blood vessel in order to obtain access to the vascular system, and may thereafter be used for guiding medical instruments such as catheters, guide wires and the like. After completion of the medical procedure, there will be an incision or a wound in the wall of the blood vessel corresponding to the size of the introducer. The bleeding from the wound, which is a result of such a surgical operation, can be stopped by applying direct pressure on the wound. However, applying direct pressure on the wound requires assistance of medical personnel and may also restrict the flow of blood through the vessel.
EP 766 947 B1 describes a haemostatic puncture device for sealing a percutaneous puncture. The main parts of this device are an anchoring means, a collagen foam acting as a sealing means, a filament means and a carrier means. The device uses an introducer or the like in order to guide the different parts to the puncture. The anchoring means, which is a narrow, rigid beam member, is introduced through the puncture to be inserted into the vessel. During the introduction, the anchoring means is in a longitudinal position in order to fit in the introducer. To function as an anchor, the anchoring means is manipulated in such a way that its end portions grip the inner edges of the puncture. The anchoring means is connected to the sealing means by the filament means in a pulley-like configuration. Thus, after the anchoring means has been put in place and the introducer has been withdrawn, the pulley-like configuration will pull the sealing means towards the puncture and eventually seal the puncture on the outside wall of the vessel. Thus, the collagen foam performs all the sealing, i.e. the puncture is only sealed on the outside wall of the vessel. The collagen foam is effective in stopping the flow of blood through the puncture wound, but the closure device according to EP 766 947 B1 has disadvantages. Besides the potential risk that the local tension applied to the edges of the puncture by the anchoring means may rupture the edges of the puncture, there is a potential risk that the tension in the filament means will cause the filament means to rupture through the anchoring means, thereby leaving the anchoring means loose inside the vessel. Furthermore, the use of a sealing device that seals on the outside of the vessel only enhances this potential problem, because an outer sealing requires a higher sealing force, i.e. a higher tension in the filament means, than a corresponding inner sealing.
Another sealing device is disclosed in U.S. Pat. No. 4,852,568. This device comprises a retraction filament fixedly secured to a plug means to be introduced into the vessel by an introducer means. When the plug means, which is made of a material being absorbable by the body, has been introduced into the vessel, the retraction filament is pulled until the engagement surface of the plug means is in intimate engagement with the interior of the artery wall. In order to hold the closure in place, the filament is held taut and is secured in position on the patient's skin, such as by use of a strip of conventional tape. Unlike the sealing means disclosed in EP 766 947 B1, the plug means according to U.S. Pat. No. 4,852,568 seals the puncture on the inside of the vessel wall. However, the risk that the fastening means, in this case a filament such as a very thin thread, which must be pulled with considerable force and which is then left tightened for a time period being as long as several days or even weeks, ruptures through the plug means is still present. Furthermore, the risk may be enhanced by the fact that the plug means according to U.S. Pat. No. 4,852,568 is made of an absorbable (e.g. biodegradable) material that also is resilient (a preferred material according to U.S. Pat. No. 4,852,568 is Gelfoam, a porous, absorbable gelatine sold by Johnson & Johnson, Inc.) since such materials usually are known to have low rupture strength.
Through U.S. Pat. No. 5,350,399 is disclosed another sealing device for sealing a puncture in the wall of a blood vessel. This sealing device comprises an intra-arterial occluder and an extra-arterial occluder, which, in a sealing position, are held together by a guide means being integral with and extending centrally from the intra-arterial occluder. According to U.S. Pat. No. 5,350,399, the guide means, which can be in the form of an elongated flexible wire, as well as the occluders can be made from a bioabsorbable material. Further, each occluder is formed of a material and has a shape so as to be circumferentially collapsible from a normal position, and should be resiliently expandable from the collapsed state to the normal position. As stated above, bioabsorbable materials having these properties are often characterized by having low rupture strength, and the risk that the fastening means, in this case in the form of a guide means, will rupture through the intra-arterial occluder is still present.
The problem that a retaining member ruptures through an intra-arterial sealing member is also recognized in EP 474 752 B2, whose aim is to provide an occlusion assembly with which it is possible to apply more tension to the retaining element. The occlusion assembly according to EP 474 752 B2 comprises an occlusion member to be fitted against the inner wall of a vessel, a locking member to be fitted against the outer vessel wall, and a retaining element connecting the occlusion member and the locking member, so that, in use, the portion of the retaining element which passes through the wall of the blood vessel between the locking member and the occlusion member is in tension. Although no numbers for the size of this tension are given in the application, it can be assumed—both from the above stated aim of the invention and from the fact that the occlusion assembly according to EP 474 752 B2 seals a puncture in the wall of a vessel by clamping the vessel wall between the occlusion member and the locking member—that there is a considerable tension applied to the retaining element, with the accompanying risk for rupture of the occlusion member.
In this context, it should be noted that the problem that an inner seal, i.e. a sealing member designed to be positioned against the inner wall of a blood vessel, will come loose in the artery has severe implications both on long and short terms. If the retaining means ruptures through the inner seal during the introduction or shortly after its introduction, i.e. before haemostasis is obtained, the immediate problem is, of course, to stop the flow of blood through the puncture wound. For this incident, when a sealing operation is carried out using this type of intra-arterial occluder, a device for applying external compression pressure on the puncture site is often kept prepared as a precaution. If, however, the retaining means ruptures through the inner seal when haemostasis already is obtained, the problem is that the inner seal can follow the flow of blood to a position where the artery is so narrow that the inner seal occludes the blood vessel, which may necessitate amputation of the part of the body in which the inner seal has got stuck. Having in mind that it normally takes several months before the body actually absorbs arterial sealing devices being made of an absorbable material, it is easy to realize that the long-term requirements regarding the rupture strength of such sealing devices are quite severe.
It should also be noted that a requirement for an intra-arterial sealing device is that it is resilient, since it usually has to be folded, collapsed or in some other way deformed in order to fit in some kind of introducer means before the introduction through the puncture hole and into the vessel. When positioned inside the vessel, the sealing device is unfolded or expanded so as to seal the puncture in the vessel wall. In other words, the diameter of the sealing device must be smaller than the diameter of the puncture hole in the introduction phase, whereas the diameter of the sealing device must be larger than the diameter of the puncture hole in the sealing phase. Generally speaking, the problem is that absorbable (e.g. biodegradable) materials having these properties, i.e. being characterized by having a low modulus, usually also are characterized by having low rupture strength. The rupture strength referred to herein relates to the force needed to displace an implanted object, which is fixed by some fastening or retaining means, such as sutures, filaments, screws or other fasteners or retainers used to fix the object in position relative to the surrounding soft or hard tissue, or the force needed to displace the fastening or retaining means once stitched through the implanted object. The rupture strength of a material is related to the modulus (commonly also referred to as the elastic modulus or Young's modulus) of the material, so that a low modulus material is characterized by having low rupture strength. A high modulus material has a higher resistance to force.
Additional general background is set forth in U.S. patent application Publication Ser. No. 2002/0,019,648A1, whose entire contents are incorporated herein by reference.